// tutorial02.c
// A pedagogical video player that will stream through every video frame as fast as it can.
//
// Code based on FFplay, Copyright (c) 2003 Fabrice Bellard, 
// and a tutorial by Martin Bohme (boehme@inb.uni-luebeckREMOVETHIS.de)
// Tested on Gentoo, CVS version 5/01/07 compiled with GCC 4.1.1
// Use
//
// gcc -o tutorial02 tutorial02.c -lavformat -lavcodec -lz -lm `sdl-config --cflags --libs`
// to build (assuming libavformat and libavcodec are correctly installed, 
// and assuming you have sdl-config. Please refer to SDL docs for your installation.)
//
// Run using
// tutorial02 myvideofile.mpg
//
// to play the video stream on your screen.

#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h> 


#include <SDL/SDL.h>
#include <SDL/SDL_thread.h>

#ifdef __MINGW32__
#undef main /* Prevents SDL from overriding main() */
#endif

#include <stdio.h>

int img_convert(AVPicture *dst, int dst_pix_fmt,  
                const AVPicture *src, int src_pix_fmt,  
                int src_width, int src_height)  
{  
    int w;  
    int h;  
    static struct SwsContext *pSwsCtx;  

  
    w = src_width;  
    h = src_height;  
    pSwsCtx = sws_getContext(w, h, src_pix_fmt,  
                            w, h, dst_pix_fmt,  
                            SWS_BICUBIC, NULL, NULL, NULL);  
  
    sws_scale(pSwsCtx, (const uint8_t* const*)src->data, src->linesize,  
            0, h, dst->data, dst->linesize);  
 
 
    return 0;  
} 


int main(int argc, char *argv[]) 
{
	AVFormatContext *pFormatCtx;
	int             i, videoStream;
	AVCodecContext  *pCodecCtx;
	AVCodec         *pCodec;
	AVFrame         *pFrame; 
	AVPacket        packet;
	int             frameFinished;
	float           aspect_ratio;

	SDL_Overlay     *bmp;
	SDL_Surface     *screen;
	SDL_Rect        rect;
	SDL_Event       event;

	if(argc < 2) 
	{
		fprintf(stderr, "Usage: test <file>\n");
		exit(1);
	}
	// Register all formats and codecs
	av_register_all();

	if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) 
	{
		fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError());
		exit(1);
	}

	// Open video file
	pFormatCtx = avformat_alloc_context();
	if(avformat_open_input(&pFormatCtx, argv[1], NULL, NULL)!=0)
		return -1; // Couldn't open file

	// Retrieve stream information
	if(av_find_stream_info(pFormatCtx)<0)
		return -1; // Couldn't find stream information

	// Dump information about file onto standard error
	av_dump_format(pFormatCtx, 0, argv[1], 0);

	// Find the first video stream
	videoStream=-1;
	for(i=0; i<pFormatCtx->nb_streams; i++)
	{
		if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO) 
		{
			videoStream=i;
			break;
		}
	}
	if(videoStream==-1)
		return -1; // Didn't find a video stream

	// Get a pointer to the codec context for the video stream
	pCodecCtx=pFormatCtx->streams[videoStream]->codec;

	// Find the decoder for the video stream
	pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
	if(pCodec==NULL) 
	{
		fprintf(stderr, "Unsupported codec!\n");
		return -1; // Codec not found
	}

	// Open codec
	if(avcodec_open(pCodecCtx, pCodec)<0)
		return -1; // Could not open codec

	// Allocate video frame
	pFrame=avcodec_alloc_frame();

	// Make a screen to put our video
#ifndef __DARWIN__
	    screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 0, 0);
#else
	    screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 24, 0);
#endif
	if(!screen) 
	{
		fprintf(stderr, "SDL: could not set video mode - exiting\n");
		exit(1);
	}

	// Allocate a place to put our YUV image on that screen
	bmp = SDL_CreateYUVOverlay(pCodecCtx->width,
				 pCodecCtx->height,
				 SDL_YV12_OVERLAY,
				 screen);

	// Read frames and save first five frames to disk
	i=0;
	while(av_read_frame(pFormatCtx, &packet)>=0) 
	{
		// Is this a packet from the video stream?
		if(packet.stream_index==videoStream) 
		{
			// Decode video frame
			avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
			  
			  // Did we get a video frame?
			if(frameFinished)
			{
				SDL_LockYUVOverlay(bmp);

				AVPicture pict;
				pict.data[0] = bmp->pixels[0];
				pict.data[1] = bmp->pixels[2];
				pict.data[2] = bmp->pixels[1];

				pict.linesize[0] = bmp->pitches[0];
				pict.linesize[1] = bmp->pitches[2];
				pict.linesize[2] = bmp->pitches[1];

				// Convert the image into YUV format that SDL uses
				img_convert(&pict, PIX_FMT_YUV420P,
				                (AVPicture *)pFrame, pCodecCtx->pix_fmt, 
					    pCodecCtx->width, pCodecCtx->height);

				SDL_UnlockYUVOverlay(bmp);

				rect.x = 0;
				rect.y = 0;
				rect.w = pCodecCtx->width;
				rect.h = pCodecCtx->height;
				SDL_DisplayYUVOverlay(bmp, &rect);
				  
			}
		}

		// Free the packet that was allocated by av_read_frame
		av_free_packet(&packet);
		SDL_PollEvent(&event);
		switch(event.type) 
		{
			case SDL_QUIT:
				SDL_Quit();
				exit(0);
				break;
			default:
				break;
		}
	}

	// Free the YUV frame
	av_free(pFrame);

	// Close the codec
	avcodec_close(pCodecCtx);

	// Close the video file
	av_close_input_file(pFormatCtx);

	return 0;
}
